A complete set of equations for determining the energy levels and the wavefunc-tions with different symmetry of electronic states of the ideal divacancy in cubic semiconductors is obtained using the Koster-Slater Green's function method. Using an empirical tight binding Hamiltonian for the band structure of the host and the on-site pertubation approximation for the defect, only the on-site and the off-site Green's functions of the host and their derivatives with respect to energy E are involved in these equations.